The very substantial increase in clock frequencies of central computer and processing devices in recent years together with the manyfold increase in data processing speeds and the requirement for transmitting much increased quantities of data have produced a commensurate need to increase signal transmission speed and to transmit a series of signals in parallel. In addition, the inexorable trend to miniaturization also dictates that electrical connectors for such applications have large numbers of densely packed signal contacts.
However, with increasing signal speed "cross-talk" between adjacent signal contacts increases creating noise which causes erroneous operation.
There is, therefore, a requirement for an electrical connector incorporating means for keeping cross-talk to an acceptably low level while transmitting high-speed signals.
One example of a known connector assembly is disclosed in Japanese patent publication 2-223172 and shown in FIGS. 13(a) and 13(b) which are schematic perspective views of a pair of shielded connectors for transmitting data at high speed.
In first and second connectors 10 and 20, first signal contacts 11 and 21, respectively, are mounted in housings 1 and 2, respectively, surrounded by first and second tubular ground contacts 12 and 22, the latter being enclosed by a dielectric 23, such as a TEFLON (trademark). On mating the connectors 10 and 20, first and second signal contacts 11 and 21 and first and second ground contacts 12 and 22, respectively, are connected with the mating parts of the first and second signal contacts enclosed and shielded by the first and second tubular ground contacts, preventing cross-talk.
However, the requirements for the connectors to be multi-pin, but also miniaturized are inherently conflicting as such necessitates a large number of signal contacts to be arrayed at extremely small pitch for example 1 mm while being enclosed by the tubular ground contacts which are also extremely small and must therefore be manufactured to high tolerances, while, additionally, the dielectric 23 must also be extremely small and precisely dimensioned.
In practice, it is very difficult to adhere to such high manufacturing tolerances in the mass production environment, with the result that the connectors are produced in undesirably large sizes.